Liver – Anatomy and Function of the Human Liver Sinusoids and Bile Canaliculi Full Liver Description [Continued from above] . . . of growing as quickly as a cancerous tumor to restore its normal size and function. Anatomy of the Liver Gross Anatomy The liver is a roughly triangular organ that extends across the entire abdominal cavity just inferior to the diaphragm. Most of the liver’s mass is located on the right side of the body where it descends inferiorly toward the right kidney . The liver is made of very soft, pinkish-brown tissues encapsulated by a connective tissue capsule. This capsule is further covered and reinforced by the peritoneum of the abdominal cavity, which protects the liver and holds it in place within the abdomen. The peritoneum connects the liver in 4 locations: the coronary ligament, the left and right triangular ligaments, and the falciform ligament. These connections are not true ligaments in the anatomical sense; rather, they are condensed regions of peritoneal membrane that support the liver. The wide coronary ligament connects the central superior portion of the liver to the diaphragm.

Located on the lateral borders of the left and right lobes, respectively, the left and right triangular ligaments connect the superior ends of the liver to the diaphragm. The falciform ligament runs inferiorly from the diaphragm across the anterior edge of the liver to its inferior border. At the inferior end of the liver, the falciform ligament forms the round ligament (ligamentum teres) of the liver and connects the liver to the umbilicus. The round ligament is a remnant of the umbilical vein that carries blood into the body during fetal development. The liver consists of 4 distinct lobes – the left, right, caudate, and quadrate lobes. The left and right lobes are the largest lobes and are separated by the falciform ligament. The right lobe is about 5 to 6 times larger than the tapered left lobe. The small caudate lobe extends from the posterior side of the right lobe and wraps around the inferior vena cava. The small quadrate lobe is inferior to the caudate lobe and extends from the posterior side of the right lobe and wraps around the gallbladder.

Bile Ducts The tubes that carry bile through the liver and gallbladder are known as bile ducts and form a branched structure known as the biliary tree. Bile produced by liver cells drains into microscopic canals known as bile canaliculi. The countless bile canaliculi join together into many larger bile ducts found throughout the liver. These bile ducts next join to form the larger left and right hepatic ducts , which carry bile from the left and right lobes of the liver. Those two hepatic ducts join to form the common hepatic duct that drains all bile away from the liver. The common hepatic duct finally joins with the cystic duct from the gallbladder to form the common bile duct , carrying bile to the duodenum of the small intestine. Most of the bile produced by the liver is pushed back up the cystic duct by peristalsis to arrive in the gallbladder for storage, until it is needed for digestion. Blood Vessels The blood supply of the liver is unique among all organs of the body due to the hepatic portal vein system.

Blood traveling to the spleen , stomach , pancreas , gallbladder, and intestines passes through capillaries in these organs and is collected into the hepatic portal vein . The hepatic portal vein then delivers this blood to the tissues of the liver where the contents of the blood are divided up into smaller vessels and processed before being passed on to the rest of the body. Blood leaving the tissues of the liver collects into the hepatic veins that lead to the vena cava and return to the heart . The liver also has its own system of arteries and arterioles that provide oxygenated blood to its tissues just like any other organ. Lobules The internal structure of the liver is made of around 100,000 small hexagonal functional units known as lobules. Each lobule consists of a central vein surrounded by 6 hepatic portal veins and 6 hepatic arteries. These blood vessels are connected by many capillary-like tubes called sinusoids , which extend from the portal veins and arteries to meet the central vein like spokes on a wheel. Each sinusoid passes through liver tissue containing 2 main cell types: Kupffer cells and hepatocytes.

Kupffer cells are a type of macrophage that capture and break down old, worn out red blood cells passing through the sinusoids. Hepatocytes are cuboidal epithelial cells that line the sinusoids and make up the majority of cells in the liver. Hepatocytes perform most of the liver’s functions – metabolism, storage, digestion, and bile production. Tiny bile collection vessels known as bile canaliculi run parallel to the sinusoids on the other side of the hepatocytes and drain into the bile ducts of the liver. Physiology of the Liver Digestion The liver plays an active role in the process of digestion through the production of bile. Bile is a mixture of water, bile salts, cholesterol, and the pigment bilirubin. Hepatocytes in the liver produce bile, which then passes through the bile ducts to be stored in the gallbladder. When food containing fats reaches the duodenum , the cells of the duodenum release the hormone cholecystokinin to stimulate the gallbladder to release bile. Bile travels through the bile ducts and is released into the duodenum where it emulsifies large masses of fat.

The emulsification of fats by bile turns the large clumps of fat into smaller pieces that have more surface area and are therefore easier for the body to digest. Bilirubin present in bile is a product of the liver’s digestion of worn out red blood cells. Kupffer cells in the liver catch and destroy old, worn out red blood cells and pass their components on to hepatocytes. Hepatocytes metabolize hemoglobin, the red oxygen-carrying pigment of red blood cells, into the components heme and globin. Globin protein is further broken down and used as an energy source for the body. The iron-containing heme group cannot be recycled by the body and is converted into the pigment bilirubin and added to bile to be excreted from the body. Bilirubin gives bile its distinctive greenish color. Intestinal bacteria further convert bilirubin into the brown pigment stercobilin, which gives feces their brown color. Metabolism The hepatocytes of the liver are tasked with many of the important metabolic jobs that support the cells of the body.

Because all of the blood leaving the digestive system passes through the hepatic portal vein, the liver is responsible for metabolizing carbohydrate, lipids, and proteins into biologically useful materials. Our digestive system breaks down carbohydrates into the monosaccharide glucose, which cells use as a primary energy source. Blood entering the liver through the hepatic portal vein is extremely rich in glucose from digested food. Hepatocytes absorb much of this glucose and store it as the macromolecule glycogen, a branched polysaccharide that allows the hepatocytes to pack away large amounts of glucose and quickly release glucose between meals. The absorption and release of glucose by the hepatocytes helps to maintain homeostasis and protects the rest of the body from dangerous spikes and drops in the blood glucose level. (See more about glucose in the body .) Fatty acids in the blood passing through the liver are absorbed by hepatocytes and metabolized to produce energy in the form of ATP. Glycerol, another lipid component, is converted into glucose by hepatocytes through the process of gluconeogenesis. Hepatocytes can also produce lipids like cholesterol, phospholipids, and lipoproteins that are used by other cells throughout the body.

Much of the cholesterol produced by hepatocytes gets excreted from the body as a component of bile. Dietary proteins are broken down into their component amino acids by the digestive system before being passed on to the hepatic portal vein. Amino acids entering the liver require metabolic processing before they can be used as an energy source. Hepatocytes first remove the amine groups of the amino acids and convert them into ammonia and eventually urea. Urea is less toxic than ammonia and can be excreted in urine as a waste product of digestion. The remaining parts of the amino acids can be broken down into ATP or converted into new glucose molecules through the process of gluconeogenesis. Detoxification As blood from the digestive organs passes through the hepatic portal circulation, the hepatocytes of the liver monitor the contents of the blood and remove many potentially toxic substances before they can reach the rest of the body. Enzymes in hepatocytes metabolize many of these toxins such as alcohol and drugs into their inactive metabolites. And in order to keep hormone levels within homeostatic limits, the liver also metabolizes and removes from circulation hormones produced by the body’s own glands.

Storage The liver provides storage of many essential nutrients, vitamins, and minerals obtained from blood passing through the hepatic portal system. Glucose is transported into hepatocytes under the influence of the hormone insulin and stored as the polysaccharide glycogen. Hepatocytes also absorb and store fatty acids from digested triglycerides. The storage of these nutrients allows the liver to maintain the homeostasis of blood glucose. Our liver also stores vitamins and minerals - such as vitamins A, D, E, K, and B12, and the minerals iron and copper - in order to provide a constant supply of these essential substances to the tissues of the body. Production The liver is responsible for the production of several vital protein components of blood plasma: prothrombin, fibrinogen, and albumins. Prothrombin and fibrinogen proteins are coagulation factors involved in the formation of blood clots. Albumins are proteins that maintain the isotonic environment of the blood so that cells of the body do not gain or lose water in the presence of body fluids. Immunity The liver functions as an organ of the immune system through the function of the Kupffer cells that line the sinusoids.

Kupffer cells are a type of fixed macrophage that form part of the mononuclear phagocyte system along with macrophages in the spleen and lymph nodes . Kupffer cells play an important role by capturing and digesting bacteria, fungi, parasites, worn-out blood cells, and cellular debris. The large volume of blood passing through the hepatic portal system and the liver allows Kupffer cells to clean large volumes of blood very quickly. Prepared by Tim Taylor, Anatomy and Physiology Instructor What are Kupffer Cells? (with pictures) Hobbies What are Kupffer Cells? Last Modified Date: 12 December 2016 Copyright Protected: 10 hilariously insightful foreign words Kupffer cells are a specialized form of immune cells that exist only within the liver. They are one of several kinds of macrophages , a type of white blood cell , that help the body maintain health by destroying bacteria, old blood cells and other foreign substances that occur in the blood stream because of illness, injury or body malfunction or simply through natural aging of the various body cells. These cells develop within the bone marrow , then migrate to the liver, where they complete their development into cells specially designed to protect the liver.

These specialized cells are considered part of the reticuloendothelial system , a part of the immune system . This subdivision of the overall human immune system consists not only of the Kupffer cells, but also of immune cells located in the reticular connective tissue. Reticular connective tissue is specialized tissue that supports the lymph nodes, the spleen and the red bone marrow. It also helps support adipose tissue , or fat cells. All of these elements contribute to the complex network of cells and organs that constitute the human immune system. Originally discovered in 1876 by Karl Wilhelm von Kupffer, these cells originally were believed to originate within the liver and to constitute part of the lining of the liver's blood vessels . Additional research and observation led another scientist, Tadeusz Browicz, to realize that they were macrophages that originated not in the liver, but in the bone marrow. He made this discovery in 1898, and because of his role in their discovery and function, they are sometimes also called Browicz-Kupffer cells. Since then, scientists have discovered many of their functions, including their role in recycling dead blood cells and helping the liver respond to toxic substances in the blood stream.

As part of their normal immune function, Kupffer cells also help repair injury to the liver. They have a role in the development of cirrhosis of the liver, a serious disease characterized by scarring and excess fibrous tissue in the organ, most often caused by excessive alcohol consumption. Some triggers, including carcinogenic agents, can cause the cells to initiate production of collagen , a connective tissue, within the liver. Too much of this tissue, as well as excessive scarring in the liver, eventually renders the liver unable to perform its normal function. It also makes it impossible for the liver to regenerate itself as it does under normal circumstances. Ad Kupffer cell | anatomy | Britannica.com Kupffer cell white blood cell Kupffer cell, any of the stellate (star-shaped) cells in the linings of the liver sinusoids. The sinusoids are microscopic blood channels. The Kupffer cells are phagocytic, i.e., capable of ingestion of other cells and of foreign particles. They also store hemosiderin so that it is available for the production of hemoglobin , the oxygen-transporting component of the red blood cell .

Hemosiderin is an iron-containing pigment that is formed from the hemoglobin of red blood cells that have disintegrated. Learn More in these related articles: in human digestive system: Microscopic anatomy ...which fingerlike projections (microvilli) of the hepatocytes extend, allowing direct accessibility of the hepatocyte to the bloodstream in the sinusoids. The other major cell of the liver, the Kupffer cell, adheres to the wall of the sinusoid and projects into its lumen. It functions as a phagocyte (a cell that engulfs and destroys foreign material or other cells). Small spaces (Disse... in liver ...bile ducts and blood vessels. Hepatic cells make up about 60 percent of the tissue and perform more metabolic functions than any other group of cells in the body. A second group of cells, called Kupffer cells, line the smallest channels of the liver’s vascular system and play a role in blood formation, antibody production, and ingestion of foreign particles and cellular debris. in sinusoid ...marrow. The sinusoids form from branches of the portal vein in the liver and from arterioles (minute arteries) in other organs.

The walls of the sinusoids are lined with phagocytic cells, called Kupffer cells, that digest old red blood cells and clear the bloodstream of toxins. 3 References found in Britannica Articles Assorted References Corrections? Updates? Help us improve this article! Contact our editors with your feedback. MEDIA FOR: You have successfully emailed this. Error when sending the email. Try again later. Edit Mode Submit Tips For Editing We welcome suggested improvements to any of our articles. You can make it easier for us to review and, hopefully, publish your contribution by keeping a few points in mind. Encyclopædia Britannica articles are written in a neutral objective tone for a general audience. You may find it helpful to search within the site to see how similar or related subjects are covered. Any text you add should be original, not copied from other sources. At the bottom of the article, feel free to list any sources that support your changes, so that we can fully understand their context. (Internet URLs are the best.) Your contribution may be further edited by our staff, and its publication is subject to our final approval. Unfortunately, our editorial approach may not be able to accommodate all contributions. Submit Thank You for Your Contribution!

Our editors will review what you've submitted, and if it meets our criteria, we'll add it to the article. Please note that our editors may make some formatting changes or correct spelling or grammatical errors, and may also contact you if any clarifications are needed. Uh Oh There was a problem with your submission. Please try again later. Close Date Published: July 20, 1998 URL: Access Date: January 19, 2017 Share Where Do Stem Cells Come From? Somatic vs Embryonic Where are stem cells found in the body? Answer: Stem cells come from different places, depending on the type of stem cell you are talking about. In leukemia and lymphoma , stem cells may be transplanted into the person with cancer to help replenish the bone marrow for production of new blood cells. In these cases, the stem cells come from the bone marrow or bloodstream of a living donor. Stem cells of this type are also known as adult stem cells and, more specifically, hematopoietic stem cells, since they give rise to blood cells. The stem cell transplants performed in people with cancer do not use any embryonic cells.

When it comes to stem cell research, however, stem cells might come from any number of different sources, including from specialized tissues of living human donors or sacrificed human embryos. See "Other Stem Cells," below. Stem Cells for Transplants (HSCT) in Cancer The bone marrow makes all of your blood cells: red cells, white cells, and other cells called megakaryocytes that make platelets to help with clotting. Hematopoietic stem cells within the bone marrow are the “parents” or progenitors of all of these different cell types that form the blood. These hematopoietic stem cells are transplanted into a person with cancer to help replenish healthy bone marrow and blood cells; high doses of chemotherapy kill cancer cells effectively, but also kill stem cells in the bone marrow. So, shortly after chemotherapy, stem cells are given into a vein, much like a blood transfusion. The cells take some time to settle into the bone marrow and begin to grow and make new healthy blood cells. Bone Marrow vs. Peripheral Blood Years ago, the only source for stem cells used in transplants was bone marrow. Then a small number of blood-forming stem cells was discovered circulating out in the peripheral bloodstream.

Doctors learned to collect these stem cells from the circulating blood -- and to use them for transplants. This type of transplant, known as a peripheral blood stem cell transplant, or PBSCT, has become more common than transplants from bone marrow, however, both methods are in use today. Other Stem Cells In other cases, and in the absence of additional information, the term "stem cell" is ambiguous as to the source of the cells. Additional descriptors are needed to tell you what type of stem cell it is and where it comes from. There are currently three main categories of stem cells; each one has a different source: Embryonic stem cells are the most controversial stem cells since they come from human embryos that have been destroyed, or harvested for science. According to the National Institutes of Health (NIH) stem cells from sacrificed human embryos were first grown in a laboratory in 1998; they were originally “created for reproductive purposes,” but when they were no longer needed, they were donated with informed consent of "the donor" -- presumably the egg donor, but possibly the sperm donor -- or perhaps both -- in any case, consent obviously does not refer to the developing human embryo.

Children are usually deemed unable to provide consent for medical procedures prior to the age 16 years; sometimes 18 years of age is used as the threshold age for consent. Adult stem cells are also called somatic stem cells. These stem cells are obtained without the destruction of a human embryo. Hematopoietic or blood-forming stem cells are an example of this kind of stem cell, and they have been used for generations. The term “somatic” means “body” and underscores that these cells come from a living body and not from a sacrificed embryo. Scientists have found adult stem cells in many more tissues than once thought possible. According to the NIH, adult stem cells have been found in many organs and tissues, including brain, bone marrow, peripheral blood, blood vessels, skeletal muscle, skin, teeth, heart, gut, liver, ovarian cells, and testis. Induced pluripotent stem cells, or iPSCs, are adult cells that have been genetically reprogrammed to be more like embryonic stem cells. The source is adult or somatic cells and not embryonic cells, but these are adult cells that have undergone genetic engineering.

According to UCLA's Center for Regenerative Medicine and Stem Cell Research, iPSCs usually start out as skin cells or blood cells, which then undergo genetic programming. It is currently possible to produce almost any desired cell type from any patient's cells. Laboratory research has shown promising results using these cells to correct a number of genetic disorders of the blood, nervous system and muscles. Updated February 2016, TI. Role of Kupffer cells in host defense and liver disease. - PubMed - NCBI Role of Kupffer cells in host defense and liver disease. 1Department of Medicine II, University of Munich, Klinikum Grosshadern, Munich, Germany. manfred.bilzer@med.uni-muenchen.de Abstract Kupffer cells (KC) constitute 80-90% of the tissue macrophages present in the body. They reside within the lumen of the liver sinusoids, and are therefore constantly exposed to gut-derived bacteria, microbial debris and bacterial endotoxins, known to activate macrophages. Upon activation KC release various products, including cytokines, prostanoides, nitric oxide and reactive oxygen species.

These factors regulate the phenotype of KC themselves, and the phenotypes of neighboring cells, such as hepatocytes, stellate cells, endothelial cells and other immune cells that traffic through the liver. Therefore, KC are intimately involved in the liver's response to infection, toxins, ischemia, resection and other stresses. This review summarizes established basic concepts of KC function as well as their role in the pathogenesis of various liver diseases. PMID: The Cells in Your Body - Science NetLinks Science NetLinks The Cells in Your Body Introduction This resource provides you with an introduction to cells. Everyone’s body is made of the same basic stuff. All living things, large or small, plant or animal, are made up of cells. Most living things are made up of one cell and they are called unicellular organisms. Many other living things are made up of a large number of cells that form a larger plant or animal. These living things are known as multicellular organisms. Water makes up about two thirds of the weight of cells. Cells are very small; most cells can only be seen through a microscope. Cells are the smallest living units that are capable of reproducing themselves. Each cell in your body was made from an already existing cell.

All plants and animals are made up of cells. In this article, we will talk about the cells that make up You. All the parts of your body are made up of cells. There is no such thing as a typical cell. Your body has many different kinds of cells. Though they might look different under a microscope, most cells have chemical and structural features in common. In humans, there are about 200 different types of cells, and within these cells there are about 20 different types of structures or organelles. All cells have a membrane. Cell membranes are the outer layers that hold the cell together. They let nutrients pass into the cell and waste products pass out. Not everything can pass through a cell membrane. What gets through and what doesn’t depends on both the size of the particle trying to get in and the size of the opening in the membrane. Cells also have a nucleus. This is the cell’s control center. Cells continually divide to make more cells for growth and repair in your body. The nucleus contains the information that allows cells to reproduce, or make more cells. Another important part of a cell is the mitochondrion. This is the part of the cell where food and oxygen combine to make energy.

You know that you need air to breathe. It is the oxygen in air that your body really needs. Every cell in your body needs oxygen to help it metabolize (burn) the nutrients released from food for energy. You also know that you need food. Food gives you energy, but oxygen is needed to break down the food into pieces that are small enough for your cells to use This is known as cellular respiration and it is the process of oxidizing food molecules, like glucose, to carbon dioxide and water. The energy released is chemically trapped for use by all the energy-consuming activities of the cell. Your cells are the energy converters for your body. Different cells have different jobs to do. Each cell has a size and shape that is suited to its job. Cells that do the same job combine together to form body tissue, such as muscle, skin, or bone tissue. Groups of different types of cells make up the organs in your body, such as your heart, liver, or lungs. Each organ has its own job to do, but all organs work together to maintain your body. A group of different organs working together to do a job makes up a system.

All the systems in your body are like members of a team whose job it is to keep you alive and healthy. The different types of cells in your body have different, specialized jobs to do. The specialization of cells depends almost always on the exaggeration of properties common to cells. For example, cells that line the intestine have extended cell membranes. This increases the amount of surface area that is available to absorb food. Nerve cells can be very long, which makes them efficient in sending signals from the brain to the rest of your body. Cells in heart muscle process a lot of energy, so they have a large number of mitochondrion, the part of the cells where energy is made. Like all living things, cells die. The number of cells that an adult male loses per minute is roughly 96 million. Fortunately, in that same minute, about 96 million cells divided, replacing those that died. Just as you shed dead skin cells, dead cells from internal organs pass through and out of the body with waste products. The length of a cell’s life can vary.

For example, white blood cells live for about thirteen days, cells in the top layer of your skin live about 30 days, red blood cells live for about 120 days, and liver cells live about 18 months. Did you find this resource helpful? 666 How Many Cells Are In Your Body? – Phenomena: The Loom Posted Wed, 10/23/2013 A simple question deserves a simple answer. How many cells are in your body? Unfortunately, your cells can’t fill out census forms, so they can’t tell you themselves. And while it’s easy enough to look through a microscope and count off certain types of cells, this method isn’t practical either. Some types of cells are easy to spot, while others–such as tangled neurons–weave themselves up into obscurity. Even if you could count ten cells each second, it would take you tens of thousands of years to finish counting. Plus, there would be certain logistical problems you’d encounter along the way to counting all the cells in your body–for example, chopping your own body up into tiny patches for microscopic viewing.

For now, the best we can hope for is a study published recenty in Annals of Human Biology, entitled, with admirable clarity, “An Estimation of the Number of Cells in the Human Body.” The authors–a team of scientists from Italy, Greece, and Spain–admit that they’re hardly the first people to tackle this question. They looked back over scientific journals and books from the past couple centuries and found many estimates. But those estimates sprawled over a huge range, from 5 billion to 200 million trillion cells. And practically none of scientists who offered those numbers provided an explanation for how they came up with them. Clearly, this is a subject ripe for research. If scientists can’t count all the cells in a human body, how can they estimate it? The mean weight of a cell is 1 nanogram. For an adult man weighing 70 kilograms, simple arithmetic would lead us to conclude that that man has 70 trillion cells. On the other hand, it’s also possible to do this calculation based on the volume of cells. The mean volume of a mammal cell is estimated to be 4 billionths of a cubic centimeter.

(To get a sense of that size, check out The Scale of the Universe .) Based on an adult man’s typical volume, you might conclude that the human body contains 15 trillion cells. So if you pick volume or weight, you get drastically different numbers. Making matters worse, our bodies are not packed with cells in a uniform way, like a jar full of jellybeans. Cells come in different sizes, and they grow in different densities. Look at a beaker of blood, for example, and you’ll find that the red blood cells are packed tight. If you used their density to estimate the cells in a human body, you’d come to a staggering 724 trillion cells. Skin cells, on the other hand, are so sparse that they’d give you a paltry estimate of 35 billion cells. So the author of the new paper set out to estimate the number of cells in the body the hard way, breaking it down by organs and cell types.

(They didn’t try counting up all the microbes that also call our body home , sticking only to human cells.) They’ve scoured the scientific literature for details on the volume and density of cells in gallbladders, knee joints, intestines, bone marrow, and many other tissues. They then came up with estimates for the total number of each kind of cell. They estimate, for example, that we have 50 billion fat cells and 2 billion heart muscle cells. Adding up all their numbers, the scientists came up with…drumroll…37.2 trillion cells. This is not a final number, but it’s a very good start. While it’s true that people may vary in size–and thus vary in their number of cells–adult humans don’t vary by orders of magnitude except in the movies . The scientists declare with great confidence that the common estimate of a trillion cells in the human body is wrong. But they see their estimate as an opportunity for a collaboration–perhaps through an online database assembled by many experts on many different body parts–to zero in on a better estimate. Curiosity is justification enough to ponder how many cells the human body contains, but there can also be scientific benefits to pinning down the number too.

Scientists are learning about the human body by building sophisticated computer models of lungs and hearts and other organs. If these models have ten times too many cells as real organs do, their results may veer wildly off the mark. The number of cells in an organ also has bearing on some medical conditions. The authors of the new study find that a healthy liver has 240 billion cells in it, for example, but some studies on cirrhosis have found the disease organ have as few as 172 billion. Perhaps most importantly, the very fact that some 34 trillion cells can cooperate for decades, giving rise to a single human body instead of a chaotic war of selfish microbes, is amazing. The evolution of even a basic level of multicellularity is remarkable enough . But our ancestors went way beyond a simple sponge-like anatomy, evolving a vast collective made of many different types. To understand that collective on a deep level, we need to know how big it really is.

Related 61 thoughts on “How Many Cells Are In Your Body?” David Sanders says: Macrophage | definition of macrophage by Medical dictionary Macrophage | definition of macrophage by Medical dictionary macrophage [mak´ro-fāj] any of the large, mononuclear, highly phagocytic cells derived from monocytes , occurring in the walls of blood vessels (adventitial cells) and in loose connective tissue (histiocytes, phagocytic reticular cells). They are components of the reticuloendothelial system . Macrophages have their origin in the bone marrow, where they pass through the monoblast and promonocyte stages to the monocyte stage; the monocytes enter the blood and then the tissues, where they become macrophages. Macrophages are usually immobile but become actively mobile when stimulated by inflammation . Their functions include phagocytosis and pinocytosis , presentation of antigens to T and B lymphocytes, and secretion of a variety of products, including enzymes, several complement components and coagulation factors, some prostaglandins and leukotrienes, and several regulatory molecules. See also immunity . A macrophage ingests an antigen.

From Polaski and Tatro, 1996. alveolar m's rounded, granular, mononuclear phagocytes within the alveoli of the lungs that ingest inhaled particulate matter. armed m's those capable of inducing cytotoxicity as a consequence of antigen binding by cytophilic antibodies on their surfaces or by factors derived from T lymphocytes . mac·ro·phage (mak'rō-fāj), Avoid the mispronunciation mak'ro-fahzh. Any mononuclear, actively phagocytic cell arising from monocytic stem cells in the bone marrow; these cells are widely distributed in the body and vary in morphology and motility, although most are large, long-lived cells with nearly round nuclei and abundant endocytic vacuoles, endosomes, lysosomes, and phagolysosomes.

Phagocytic activity is typically mediated by serum recognition factors, including certain immunoglobulins and components of the complement system, but also may be nonspecific for some inert materials and bacteria, as in the case of alveolar macrophages; macrophages also are involved in cell-mediated immune responses, participate in presenting antigens to lymphocytes, secrete a variety of immunoregulatory molecules, and interact with natural killer cells. [macro- + G. phagō, to eat] macrophage /mac·ro·phage/ (mak´ro-fāj) any of the large, mononuclear, highly phagocytic cells derived from monocytes that occur in the walls of blood vessels (adventitial cells) and in loose connective tissue (histiocytes, phagocytic reticular cells). They are components of the reticuloendothelial system. Macrophages are usually immobile but become actively mobile when stimulated by inflammation; they also interact with lymphocytes to facilitate antibody production. alveolar macrophage one of the rounded granular, mononuclear phagocytes within the alveoli of the lungs that ingest inhaled particulate matter.

armed macrophages those capable of inducing cytotoxicity as a consequence of antigen-binding by cytophilic antibodies on their surfaces or by factors derived from T lymphocytes. macrophage [mak′rəfāj] Etymology: Gk, makros + phagein, to eat a granular mononuclear phagocyte that circulates as a monocyte in the blood and resides in all tissues. Macrophages recognize and engulf foreign materials and present fragments or epitopes on their membranes to initiate an immune response. Macrophages have many names, for instance histiocytes, reticuloendothelial cells, Kupffer cells in the liver, littoral cells in the spleen. Macrophages are the single most abundant cell in the human body, more numerous than skin cells or red blood cells. See also Kupffer cells , phagocyte , reticuloendothelial system . Macrophage macrophage A nonspecific immune defence cell that interacts with proteins and polysaccharide antigens, internalising and partially degrading them, and/or presenting the antigens to T cells in a major histocompatibility complex (MHC) context.

Macrophages are involved in secretion, immune interaction with T and B cells and provide lymphokine receptors; once activated, macrophages are highly microbicidal and tumouricidal, often closely associated with the blood vessels, epithelium and mesothelium, which are appropriate sites for non-specific immunocytes. Morphology Large (15–80 µm in diameter), often with bleb-like or filiform pseudopodia; one (or rarely more) round to oval, occasionally indented nucleus; nuclear membrane is distinct; nuclear chromatin is fine with a reticular pattern; abundant, pale grey-blue, often granulated (coarse azurophilic granules) and vacuolated cytoplasm with phagocytosed material (RBCs, WBCs, platelets, nuclei, bacteria and remnants in native or degraded form).

mac·ro·phage (mak'rō-fāj) Any mononuclear, actively phagocytic cell arising from monocytic stem cells in bone marrow; these cells are widely distributed and vary in morphology and motility; most are large, long-lived cells with nearly round nuclei and abundant endocytic vacuoles, lysosomes, and phagolysosomes. Phagocytic activity is typically mediated by serum recognition factors, including certain immunoglobulins and components of the complement system, but also may be nonspecific for some inert materials and bacteria, as in the case of alveolar macrophages; macrophages also are involved in both the production of antibodies and in cell-mediated immune responses, participate in presenting antigens to lymphocytes, and secrete a variety of immunoregulatory molecules. [macro- + G. phagō, to eat] macrophage (mak'ro-faj?) [ macro- + -phage] MACROPHAGE: with aggregated hemosiderin granules (×500) A monocyte that has left the circulation and settled and matured in a tissue.

Macrophages are found in large quantities in the spleen, lymph nodes, alveoli, and tonsils. About 50% of all macrophages are found in the liver as Kupffer cells. They are also present in the brain as microglia, in the skin as Langerhans cells, in bone as osteoclasts, as well as in serous cavities and breast and placental tissue. Along with neutrophils, macrophages are the major phagocytic cells of the immune system. They have the ability to recognize and ingest foreign antigens through receptors on the surface of their cell membranes; these antigens are then destroyed by lysosomes. Their placement in the peripheral lymphoid tissues enables macrophages to serve as the major scavengers of the blood, clearing it of abnormal or old cells and cellular debris as well as pathogenic organisms. Macrophages also serve a vital role by processing antigens and presenting them to T cells, activating the specific immune response. They also release many substances that participate in inflammation, including chemokines and cytokines, lytic enzymes, oxygen radicals, coagulation factors, and growth factors.

See: illustration; chemokine ; cytokine ; inflammation ; oxygen radical illustration macrophage An important cell in the immune system. Macrophages are scavenging cells, large PHAGOCYTES derived from blood MONOCYTES , and are found all over the body, especially in the liver, lymph nodes, spleen and bone marrow. Some are stationary within the tissues (fixed macrophages), others are free and move about, being attracted to sites of infection. Connective tissue (fixed) macrophages are called histiocytes; those in the liver are called Kupffer cells; and those in the nervous system are called microglial cells. Macrophages are AMOEBOID and ingest foreign material and bacteria, which they destroy. In order to bring about an immune response, most ANTIGENS must first be processed by macrophages so that their antigenic elements can be presented to LYMPHOCYTES on the macrophage surfaces. The term derives from the Greek macros , large and phageo to eat. macrophage a type of scavenger cell that is widely distributed in large numbers in vertebrate tissues and which is derived from MONOCYTE blood cells.

Its function is to remove debris, which it engulfs by PHAGOCYTOSIS , and it is capable of movement by means of PSEUDOPODIA . Macrophages occur in connective tissue, lymph and blood, and one of their important roles is the digestion of old and damaged red blood cells in the spleen. Some macrophages are free-moving, others are located in fixed locations (e.g. KUPFFER CELLS ), the whole arrangement forming the RETICULOENDOTHELIAL SYSTEM . Macrophage A large white blood cell, found primarily in the bloodstream and connective tissue, that helps the body fight off infections by ingesting the disease-causing organism. HIV can infect and kill macrophages.

Mentioned in: AIDS , AIDS Tests , Echinacea , Leishmaniasis macrophage large, mononuclear, amoeboid phagocytic and multifunctional cell; has a major role in inflammation and tissue repair (identifies and engulfs dead/damaged cells, destroys microorganisms, synthesizes and releases chemical mediators of inflammation, initiates immune response to invading microorganisms, initiates tissue regeneration [releases growth factors and chemoattractants for fibroblasts] involved in tissue repair) mac·ro·phage (mak'rō-fāj) Any mononuclear, actively phagocytic cell arising from monocytic stem cells in bone marrow; widely distributed in body and vary in morphology and motility. [macro- + G. phagō, to eat] macrophage (mak´rəfāj), n any phagocytic cell of the reticuloendothelial system including specialized Kupffer's cells in the liver and spleen, and histiocytes in loose connective tissue. See also histiocyte and monocyte .

macrophage, alveolar, n a dust cell, coniophage, a vigorously phagocytic macrophage on the epithelial surface of lung alveoli where it ingests inhaled particulate matter. macrophage any of the large, mononuclear, highly phagocytic cells derived from bone marrow cells, promonocytes, the progeny of which, the monocytes, enter the bloodstream, where they stay for a few days before entering the tissues and developing into macrophages. They are components of the monocyte-macrophage system. Macrophages are usually immobile but become actively mobile when stimulated by inflammation, immune cytokines and microbial products. They are an important class of antigen presenting cells (APCs). See also immunity .

activated macrophage under the influence of cytokines, particularly γ-interferon and interleukin 4, released by antigen-stimulated Th1 lymphocytes, resting macrophages are activated whereby they become larger, more motile, stickier, express more MHCII proteins on their surface, contain more lysosomes and lysosomal enzymes, and secrete a variety of substances including interleukin 1, tumor necrosis factors; they have increased phagocytic activity and increased killing via reactive oxygen intermediates, collagenases and lysosomal enzymes. Called also angry macrophage. macrophage activating factor (MAF) BBC Science & Nature - Human Body and Mind - Organ Layer Location: Under your diaphragm, more to the right side of your body Physical description: Wedge-shaped, spongy organ Function: To get rid of toxins, to regulate your blood sugar levels and to produce bile Largest internal organ Your liver is your largest internal organ. A big blood vessel, called the portal vein, carries nutrient-rich blood from your small intestine directly to your liver. Chemical processing factory Hepatic cells make up about 60 percent of your liver tissue.

These specialised liver cells carry out more chemical processes than any other group of cells in your body. They change most of the nutrients you consume into forms your body cells can use. They Convert sugars and store and release them as needed, thereby regulating your blood sugar level Break down fats and produce cholesterol Remove ammonia from your body and produce blood proteins, including blood clotting factors Other functions of your hepatic cells are to Detoxify drugs and alcohol Produce bile, which breaks down fats in the food your eat Security guard A second important group of liver cells are the Kupffer cells. They Remove damaged red blood cells Destroy microbes and cell debris Essential for life Because your liver fulfils so many vital functions, you would die within 24 hours if it stopped working. A common sign of a damaged liver is jaundice, a yellowness of your eyes and skin. This happens when bilirubin, a yellow breakdown product of your red blood cells, builds up in your blood.

Question: Where in the human body are the Kupffer Cells to be found?
Answer: LIVER